The present invention relates to a device and method for closing a passage through which fluid flows, and more particularly, to a device and method for automatically closing a gas pipe through which inflammable gas flows during an emergency, such as when a fire breaks out.
Inflammable gas, such as propane or natural gas, flows through a gas pipe, such as a town gas pipe. A typical gas pipe used in buildings includes a gas meter incorporating a closing mechanism and a manual valve. When a fire breaks out, an indoor fire detector provides a detection signal to the closing mechanism of the gas pipe. In response to the detection signal, the gas closing mechanism closes the passage of gas. The manual valve may also be manually operated to stop the flow of gas.
However, the prior art has problems that are described below.
(1) There is a need to wire for electrically connecting the gas meter, which is located outdoors, and the fire detector, which is located indoors. Wiring is a burdensome work and may limit the location for installation of the gas meter.
(2) When the fire detector is erroneously activated, the closing mechanism closes the gas pipe.
(3) To reduce the weight of the gas meter and save costs, a case made of synthetic resin may be used to house the gas meter. In such a case, the high temperature during a fire may cause the gas meter to fall off from the pipe. As a result, the closing mechanism of the gas meter may not function effectively.
(4) When a fire breaks out in the vicinity of the gas meter, no one would be able to approach the manual valve. Therefore, it may be difficult to close the manual valve immediately after a fire breaks out.
U.S. Pat. No. 4,619,284 granted to Delarue et al. describes a prior art pyrotechnic valve arranged in a fuel valve for an aircraft. The pyrotechnic valve is electrically operated and thus needs to be wired.
U.S. Pat. No. 3,955,589 granted to Beazley describes a prior art valve that uses the urging force of a spring to drive a valve body. The valve includes a fusible cap that is melted by heat. The urging force of the spring closes the valve with the valve body when the fusible cap melts. However, this valve can be used only once. Further, a spring for moving the valve body is necessary. Thus, the structure of the valve is complicated.
U.S. Pat. No. 4,072,159 granted to Kurosawa describes a prior art valve that has a valve body and a thermal foamable plastic. When heated, the thermal foamable plastic expands and closes the valve body. However, the thermal foamable plastic has slow expansion speed, weak expansion force, and low temperature sensitivity. Therefore, the Kurosawa valve is not appropriate for use when the pipe must rapidly be closed during an emergency.